Regulation of the proteasome by Fbxo7

点击翻译按钮获取中文摘要

Living cells are largely constructed from a multitude of different proteins, each with their own individual functions and properties. Just like the components of any man-made machine, these proteins are susceptible to "wear and tear" and can become damaged over time. The health of a cell, and consequently the whole organism to which it belongs depends on the timely and specific removal of damaged proteins to prevent their accumulation in toxic aggregates that will eventually poison the cell. Cells have evolved a mechanism to identify and then destroy unwanted proteins, called the "ubiquitin-proteasome system". Damaged proteins are marked with chains of small ubiquitin molecules, targeting them to the proteasomes, the cell's "recycling bins". The failure of this system to clear protein aggregates has been linked to multiple human diseases, including Parkinson's disease, Alzheimer's disease, type II diabetes and is also implicated in those involving prion proteins which cause Creutzfeldt-Jakob disease in humans, BSE in cattle and scrapie in sheep and goats. Conversely, over-activity of the ubiquitin-proteasome system has been linked with various muscle atrophy diseases, it is therefore clear that proper regulation of this system is required for the maintenance of health.Recently, a study detailing the properties of a controller of the rate at which the proteasomes operate has been published. This protein, called PI31, has been shown to both increase and decrease proteasome activity under different circumstances. However, PI31 does not act alone. We have identified a protein called Fbxo7 that is not only capable of marking proteins for destruction with ubiquitin but which also binds to PI31. Studies in fruit flies have shown that this interaction enhances the ability of PI31 to regulate the proteasomes, and flies lacking their analgous Fbxo7 protein, which is called nutcracker, have reduced proteasome activity, and causes sterility in male flies. We have found that loss of the Fbxo7 in mice also affects their fertility. Furthermore, mutations in the human Fbxo7 gene have also been linked to Parkinson's disease, suggesting that Fbxo7 may also cooperate with PI31 to regulate proteasome activity in mammalian systems.We want to understand in detail how Fbxo7 participates in the regulation of proteasome activity in mammalian cells. We will use a variety of methods to investigate the relationship between PI31 and Fbxo7, determining whether the interaction between these two proteins affects their ability to regulate proteasome activity and mark proteins for degradation, respectively. We will also determine how the loss or over-representation of Fbxo7 in cells affects proteasome activity in cells using a range of assays both in cell lines and in an mouse model. By doing experiments to broaden our understanding of the protein degradation machinery, we hope to be able to affect and ultimately direct these processes in clinically relevant settings.